Mechanical support structure with alternative modes of high stability and low thermal conductivity, and a connecting strut

ABSTRACT

A mechanical support structure has at least one molded component made of a shape memory alloy, which in a first operating mode of the support structure yields an increase in the stability of the support structure and in a second operating mode yields a reduction in the thermal conductivity of the support structure. A strut structure is enclosed by a tubular structure which possesses a higher level of mechanical stability than the strut structure. The strut structure s permanently fastened to the tubular structure at a first end. The strut structure is connected to a mounting element. The tubular structure is separably connected to the mounting element and the strut structure at a second end of the strut structure via the at least one molded component.

BACKGROUND AND SUMMARY OF THE INVENTION

[0001] This application claims the priority of German Application DE 101 02 330.8, filed Jan. 19, 2001, the disclosure of which is expressly incorporated by reference herein.

[0002] The present invention relates to a mechanical support structure with alternative modes of high stability and low thermal conductivity, and a connecting strut that is equipped with such a support structure.

[0003] Support structures of this type are already known from the state of the art. For example, U.S. Pat. No. 3,814,361 describes a support system comprised of shunt elements inserted one inside the other, wherein outer, adjacent shunt elements that form a second strut structure and guarantee a high degree of mechanical stability can be pulled away via cooling, leaving only an inner shunt element as a first strut structure to bear the entire mechanical load; in this, the first strut structure remains engaged with the second strut structure, and, due to the small contact surface existing with one of the shunt elements, guarantees a low level of thermal conductivity. However, the second strut structure remains engaged with the first such that it can slide into and out of it, thus only a very limited degree of mechanical stability can be guaranteed, and the danger, e.g. of tilting, cannot be excluded.

[0004] Another support structure is described in European Patent Document EP 0 584 697. Here, molded components made from a shape memory alloy are used to disengage a support path that has a high degree of mechanical stability. In this case, either a support path formed by eyelets is disengaged and partially replaced with a spring mounting by extending a pin, or an expanding frame as a second strut structure, which remains permanently connected to an object as a mounting element, is opened, and thus is separated from a first strut structure in the form of a mechanically less stable strut, at the end of which the expanding frame is engaged. The second strut structure is arranged next to the first strut structure, in the same plane, which also permits only a limited degree of stability to be guaranteed.

[0005] An object of the present invention is thus to produce a mechanical support structure that will provide increased stability while maintaining a reduction in thermal conductivity in one of the operating modes. Furthermore, the support structure should be easily integrated into existing support structures.

[0006] This object is attained, according to certain preferred embodiments of the invention, by providing a mechanical support structure with at least one molded component made of a shape memory alloy, which in a first operating mode of the support structure yields an increase in stability of the support structure, and in a second operating mode yields a reduction in thermal conductivity of the support structure, wherein a strut structure is enclosed by a tubular structure, which has a higher mechanical stability as compared with the strut structure; and wherein the strut structure is permanently fastened at a first end to the tubular structure, an opposite second end of the strut structure being connected to a mounting element, and wherein the tubular structure is separably connected at the second end of the strut structure to the mounting element via the at least one molded component

[0007] The mechanical support structure specified in the invention comprises at least one molded component made of a shape memory alloy, which in a first operating mode of the support structure increases the stability of the support structure, and in a second operating mode reduces the thermal conductivity of the support structure. A strut structure is enclosed by a tubular structure that possesses a higher degree of mechanical stability as compared with the first strut structure, wherein the tubular structure that encloses the strut structure naturally increases the stability of the arrangement. In addition, the strut structure is permanently fastened at a first end to the tubular structure, so that the two structures cannot shift relative to one another; this also serves to increase the stability and to reduce the movable mass of the device. Furthermore, the strut structure is fastened to a mounting element, and the tubular structure is separably connected to the mounting element and the strut structure, at a second end of the strut structure, via the at least one molded component. This provides the strut structure with further support; in addition, the fact that the separable connection between the tubular structure on one hand and the strut structure and mounting element on the other hand is located directly at the end of the strut structure allows the release of the connection to be limited to the smallest possible spatial area, leaving the remaining design of the support structure in both modes of the structure largely unchanged.

[0008] By separating the tubular structure from the mounting element and from the second end of the strut structure, the thermal conductivity of the entire support structure can be reduced, under the control of the at least one molded component, which can be specially designed and optimized for this purpose.

[0009] In a further development of the invention, the tubular structure can be separably fastened to the mounting element and the strut structure via an interlocking clamping joint. This represents a particularly simple form of separable connection. In this arrangement, at least one clamping element, which is able to shift lengthwise along the tubular structure, can be positioned at the second end of the strut structure; this clamping element is fastened to the at least one molded component; when the shape memory alloy of the molded component is in a first state, the clamping element operates in conjunction with the clamping joint to release the clamping joint, and when the shape memory alloy of the molded component is in a second state, the clamping element operates in conjunction with the clamping joint to engage the clamping joint in an interlocking connection. In this manner, controlled by the state of the molded component, a release or engaging of the clamping joint is achieved via a simple process.

[0010] The clamping element can, for example, be designed as a cup-shaped sleeve. This must then generally be arranged or designed such that it will enable a firm connection between the strut structure and the mounting element. For example, the strut structure may be equipped with one or more extensions, which project through openings in the sleeve, and which are inseparably connected to the mounting element. The clamping joint, in turn, may be formed by at least one flexible extension of the mounting element, which interlocks into at least one recess in the tubular structure. Flexible, in this connection, means that the at least one extension of the mounting element must be sufficiently movable to permit an interlocking release and engagement of the clamping joint.

[0011] The strut structure may also be designed, at least in sections, as a hollow strut, which at least partially encloses at least one molded component. This makes it possible for the strut structure to stabilize the molded component within the support structure in a simple manner.

[0012] The at least one molded component may be of any suitable design that will trigger the shape memory effect of the molded component if the surrounding temperature exceeds or goes below a certain threshold temperature, thereby triggering a release and engagement of the separable connection to the tubular structure. Specifically, the molded components may be designed such that if the surrounding temperature exceeds or goes below a threshold temperature the molded component will be extended lengthwise, which will effect a release or engagement of the joint.

[0013] The types and embodiments of support structures described herein may be used in every suitable application. By providing for a mechanically stable operating mode and a thermally low-conductivity operating mode, any applications make sense in which, in a first phase of an operation of a device, a high degree of mechanical stability must be guaranteed, e.g. during a transport phase, and in a second phase extensive thermal insulation must be achieved, e.g. during a cooling or heating phase. Thus, the present invention is especially well suited for use in a connecting strut designed to connect components having different temperatures.

[0014] Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1a is side view of a support structure constructed in accordance with a preferred embodiment of the invention;

[0016]FIG. 1b is a side view of the support structure of FIG. 1a, shown rotated by 90°;

[0017]FIG. 1c is a longitudinal section A-A through the structure shown in FIG. 1b;

[0018]FIG. 2 is a sectional view through the structure shown in FIG. 1b, taken along section A′-A′;

[0019]FIG. 3 is an enlarged perspective view of part of a longitudinal section through one end of the support structure of FIGS. 1-2;

[0020]FIG. 4 is a perspective part cross sectional view through the support structure with a connected strut according to FIGS. 1-3; and

[0021]FIG. 5 is a perspective side view of the support structure with strut of FIG. 4.

DETAILED DESCRIPTION OF THE DRAWINGS

[0022] The support structure illustrated in FIGS. 1a through 1 c can be easily installed in the eyelet of a strut 1 or in a recess in another mounting element, in that at one end 14 of the strut structure 4, which is designed as a hollow strut, a connecting piece 2 is provided, which is inserted into such an eyelet or recess. The support structure 12 illustrated here is thus very widely applicable. In the specific case shown in FIGS. 1a through 1 c, the dimensions of the tubular structure 3 are designed to fit the strut 1, thus ideally forming an extension of the strut 1, which is designed as a tube; hence, the entire support structure 12 effectively lengthens the strut, but otherwise causes no impairment of the structure of the strut 1. This is also clearly illustrated again in FIG. 5.

[0023] Consequently, the support structure 12 is formed by a tubular structure 3 that concentrically encloses a strut structure 4. The tubular structure 3 and strut structure 4 may be separated, for example, by a thermally insulating layer which can contribute to a further stabilization of the structure in an interspace 11. With a suitable design for the connecting piece 2 and the remaining mechanism of the support structure 12, the insulating layer can also be eliminated.

[0024] At a first end 14, the tubular structure 3 and the strut structure 4 are at least firmly fastened to one another via the connecting piece 2, and are thus also connected to the adjacent strut 1. FIG. 4 shows another perspective illustration of a longitudinal section through a support structure of this type.

[0025] The function of the support structure is especially easy to recognize from the detailed view of the end 13 shown in FIG. 3. The tubular structure 3 encloses a molded component 7 in the form of a pin or a screw made of a shape memory alloy, which is held in the tubular structure 4 via a suitable seating 15. If the surrounding temperature exceeds a threshold temperature T_(s), for example T_(s)=0° C., this molded component is converted from a first state (martensite) to a second state (austenite), resulting in a change in its shape, which in the present example involves a change in length. In principle, several suitable molded components may also be incorporated. In this case, the result is a shortening of the molded component 7 in a lengthwise direction along the strut structure 4 or the tubular structure 3. This causes a sleeve 6, which in this case is cup-shaped and connected to the molded component, to shift lengthwise along the tubular structure 3 or the strut structure 4. The sleeve 6 operates a clamping joint 8 between a mounting element 5 which is permanently connected to the strut structure 4, and the tubular structure 3. In addition, the sleeve 6 has a conical projection that operates in conjunction with extensions 8A of the mounting element 5, designed, for example, as spring plates. These spring plates 8A are pressed through the sleeve 6 via a longitudinal shift of the sleeve 6 toward the first end 14, to corresponding recesses 3R in the tubular structure 3, thus an interlocking connection in the form of a clamping joint is created between the tubular structure 3 on one hand and the mounting element 5 and the strut structure 4 connected to it on the other hand, in the area of the second end 13. In this manner, a load path from the mounting element 5, through the tubular structure 3 and the strut structure 4, to the strut 1 is created. This load path possesses a high degree of mechanical stability.

[0026] If the surrounding temperature should fall below the threshold temperature T_(s), the inverse conversion of the shape memory alloy is triggered, which in the present case involves an expansion of the molded component 7. With a shifting of the sleeve 6 away from the first end 14, the clamping joint is released, and the tubular structure 3 is separated from the second strut structure 4; in this case the load path leads only through the mounting element 5 and the strut structure 4 to the strut 1. In this condition, the thermal conductivity from the mounting element 5 through the tubular structure 3 to the strut 1 is cut off, so that a significantly reduced thermal conductivity is provided.

[0027] The permanent connection between the strut structure 4 and the mounting element 5 can be produced in any suitable manner. As is shown in FIGS. 2 (in cross-section) and 3, to provide greater clarity, the strut structure 4 may, for example, be equipped with extensions 10 that project through axially cut openings 9 in the sleeve 6; the extensions 10 are not attached to the sleeve 6, so that the sleeve 6 can shift lengthwise along the extensions 10. The extensions 10 can be permanently fastened to the mounting element 5, for example, via an adhesive bond, soldering, welding, screwing, or some similar connection.

[0028] The invention can be used in any application in which different temperatures prevail on the side of the mounting element 5 than on the side of the end 14 of the support structure 12, which can be connected to another strut 1, another mounting element, or some other component. The invention may serve, for example, as a transport and operational mounting for cooling or heating devices, cooling tanks, engines, or similar devices. For example, in a space vehicle application, during the lift-off and landing phases, a high degree of mechanical stability for the seating, e.g. of cryogenic devices on one side of the support structure 12, can be guaranteed by engaging the separable connection of the support structure 12, since the high lift-off loads are supported by both the tubular structure 3 and the strut structure 4. In an operating phase out in space, the joint can then be released, causing an extensive thermal insulation of space, the joint can then be released, causing an extensive thermal insulation of the cryogenic device from the devices on the other side of the support structure 12, as specified in the invention.

[0029] The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof. 

1. Mechanical support structure with at least one molded component made of a shape memory alloy, which in a first operating mode of the support structure yields an increase in stability of the support structure, and in a second operating mode yields a reduction in thermal conductivity of the support structure, wherein a strut structure is enclosed by a tubular structure, which has a higher mechanical stability as compared with the strut structure; wherein the strut structure is permanently fastened at a first end to the tubular structure, an opposite second end of the strut structure being connected to a mounting element, and wherein the tubular structure is separably connected at the second end of the strut structure to the mounting element via the at least one molded component.
 2. Support structure according to claim 1, wherein the tubular structure is separably connected at the second end of the strut structure via an interlocking clamping joint to the mounting element and the strut structure.
 3. Support structure according to claim 2, in which at least one clamping element that can shift lengthwise along the tubular structure is positioned at the second end of the strut structure; this at least one clamping element being connected to the at least one molded component, and, when the shape memory alloy of the molded component is in a first state, the clamping element operates in conjunction with the clamping joint to release the clamping joint, and when the shape memory alloy of the molded component is in a second state, the clamping element operates in conjunction with the clamping joint to engage the clamping joint in an interlocking connection.
 4. Support structure according to claim 3, wherein the clamping element is designed as a cup-shaped sleeve, and the strut structure is equipped with extensions, which protrude through openings in the sleeve and which are inseparably fastened to the mounting element.
 5. Support structure according to claim 2, wherein the clamping joint is formed by at least one flexible extension of the mounting element, which is engaged in at least one recess in the tubular structure in an interlocking connection.
 6. Support structure according to claim 3, wherein the clamping joint is formed by at least one flexible extension of the mounting element, which is engaged in at least one recess in the tubular structure in an interlocking connection.
 7. Support structure according to claim 4, wherein the clamping joint is formed by at least one flexible extension of the mounting element, which is engaged in at least one recess in the tubular structure in an interlocking connection.
 8. Support structure according to claim 1, wherein the strut structure is designed at least in sections as a hollow strut, which at least partially encloses the at least one molded component.
 9. Support structure according to claim 2, wherein the strut structure is designed at least in sections as a hollow strut, which at least partially encloses the at least one molded component.
 10. Support structure according to claim 3, wherein the strut structure is designed at least in sections as a hollow strut, which at least partially encloses the at least one molded component.
 11. Support structure according to claim 4, wherein the strut structure is designed at least in sections as a hollow strut, which at least partially encloses the at least one molded component.
 12. Support structure according to claim 5, wherein the strut structure is designed at least in sections as a hollow strut, which at least partially encloses the at least one molded component.
 13. Support structure according to claim 1, wherein said first end of the structure is permanently fastened to a connecting strut structure which has a mounting element to thereby form a connecting strut.
 14. A support structure comprising: a first strut member, a second strut member extending adjacent the first strut member and having a first section and a second section spaced from one another along a length of the second strut member, said first section being fixed to the first strut member, and a clamping assembly operable to selectively clamp said second section to the first strut member, wherein said clamping assembly includes a thermally responsive shape memory member which selectively operates the clamping assembly as a function of temperature to thereby selectively change the rigidity and thermal conductivity of the support structure.
 15. A support structure according to claim 14, wherein said first strut member is a tubular member which surrounds the second strut member.
 16. A support structure according to claim 15, wherein said shape memory member is carried by the second strut member.
 17. A support structure according to claim 16, wherein said shape memory member is connected with a clamp member having conical clamping surfaces operable to fit the first and second strut members together at the second section when in a first thermally induced position and to release the first strut member from the second strut member at the second section when in a second thermally induced position.
 18. A support structure according to claim 14, comprising a mounting element connected to the second strut member for mounting the support structure to a cryogenic device used in a space environment. 